The present invention relates to a method of manufacturing progressive ophthalmic lenses whereof each is produced in correspondence with the individual data of a specific spectacle wearer, in accordance with the introductory clause of Patent claim 1.
Methods which the introductory clause of Patent claim 1 starts out from are known, for example, from the U.S. Pat. No. 2,878,721, the German Patent DE-A-43 37 369, the German trade journal DOZ 8/96, pp. 44 to 46, the trade journal NOJ 11/97, from page 18 onwards, or from the German Patent DE-A-1 97 01 312. In all other respects explicit reference is made to these prior art documents for an explanation of all particulars not described here in more details.
In practical operation, the procedure in the production of ophthalmic lenses is presently as followsxe2x80x94irrespectively of whether mono-focal, multi-focal or progressive ophthalmic lenses are involved:
Initially, an ophthalmic lens finished on one side, mostly xe2x80x9ca round blankxe2x80x9d, i.e. without pre-edging (in a manner specific of the mount). For reasons of manufacturing techniques, the finished surface of the ophthalmic lens complete on one side is, as a rule, the face surface; the reason for this resides in the fact that the so-called xe2x80x9cprescription lens productionsxe2x80x9d are almost exclusively equipped for machining the concave surface, i.e. the surface on the side of the eye. In the prescription lens productions, the surface on the eye side is manufactured only upon presentation of a concrete order in correspondence with the so-called prescription data of the respective spectacle wearer. In the field of progressive ophthalmic lenses, the prescription data is to be understood to denote the effect required in the so-called reference point in the distant vision range, the addition as well as possibly the amount and the axial position of an astigmatic effect.
In the progressive ophthalmic lenses common in the market at present, the face area is almost exclusively the progressive surface. The reason for this resides in the aspect that the methods of computation and manufacture usual in the past rendered an individualized computation and above all an individualized production of the progressive surface difficult at xe2x80x9cenforceable or achievablexe2x80x9d sales prices.
For this reason, a great number of so-called base graphs have been computed to xe2x80x9ccoverxe2x80x9d the usually required range of effects. This is to be understood in the sense that a certain number of different progressive surfaces has been computed which are distinguished with respect to the so-called surface refracting power in the reference point in the distant vision range and with respect to the additionxe2x80x94which is mostly defined as the difference of the surface refracting power between the reference point in the distant vision range and the near reference point. These progressive surfaces are combined with different concave surfaces on the side of the eye so that the ophthalmic lens will create the prescribed effect in the reference point in the distant vision range and in the reference point in the near vision range. In other words, a base graph always xe2x80x9ccoversxe2x80x9d a defined range of effects of several diopters.
In the computation of the individual progressive surfaces serving as base graphs or base surfaces, respectively, frequently occurring values of the individual influential parameters have been presumed, such as the pupil separation (PD or ps), the cornea/Apex distance (HAS), the convergence of the eyes when the view is lowered along the so-called main line of sight, possibly as a function of the addition, the forward inclination, the prism, etc. This does not mean anything else but that in the past xe2x80x9cindividualizedxe2x80x9d ophthalmic lenses were calculated for a xe2x80x9cfictitious average spectacle wearerxe2x80x9d whilst it was presumed that these ophthalmic lenses satisfy the majority of demands also when influential parameters at variance there from occur.
In the course of the past few years, however, substantial progress has been achieved both in the rate of optimization of a progressive area and in manufacturing technology so that it has now become possible, even at reasonable manufacturing costs, to compute and manufacture individualized ophthalmic lenses.
The U.S. Pat. No. 2,878,721 proposes to compute a progressive surface that presents also the astigmatic effect in correspondence with the respective prescription. As a logical consequence, the progressive area is the surface on the side of the eyes in accordance with that prior art document.
The German Patent DE-A-43 37 36 equally proposes an individualized progressive surface. In particular, this progressive surface may have an astigmatic effect that is matched with the respective prescription data in terms of the amount and the axial position. The progressive area may be the face surface or the surface on the side of the eyes.
In the articles quoted by way of introduction, which were published in the trade journals DOZ 8/96, pp. 44 to 46 or NOJ 11/97, from page 18 onwards, the alternative technique is proposed to achieve individualization by the provision that starting out from a standardized progressive surface, i.e. starting out from progressive surfaces in the xe2x80x9cconventional base graph gradingxe2x80x9d, the individualization is achieved by combining the progressive surfaces with individually computed non-spherical surfaces as areas on the side of the eyes.
The German Patent DE-A-197 01 312 reflects, in the last analysis, the same disclosure as the German Patent DE-A-43 37 36 or the U.S. Pat. No. 2,878,721:
In order to be able to manufacture the progressive surface in a conventional manner in the prescription lens production facilities, the area on the side of the eyes is configured as progressive surface. A spherical or non-spherical surface is used as face area, whose refracting power in the area apex is graded in a comparatively xe2x80x9ccoarsexe2x80x9d manner in correspondence with the usually employed base graphs.
All the progressive ophthalmic lenses known from the afore-quoted prior art documents share the common aspect that a very specific pairing of face surface and surface on the eye-side is used again and again for a certain xe2x80x9cprescription valuexe2x80x9d. In other words, a special distant-vision effect is always realized by a respective surface power value of the face surface and of the surface on the side of the eyes.
In accordance with the present invention it has now been found that particularly when an individualized progressive surface is combined with a spherical or non-spherical face surface, which are then graded in a comparatively coarse manner in correspondence with the common xe2x80x9cbase graphsxe2x80x9d, it is not possible to satisfy the various demands resulting from the individual physiologic conditions of the individual spectacle wearers or the respective conditions of use, respectively.
On the other hand, the use of two progressive surfaces suitable to overcome a number of the disadvantages of the progressive ophthalmic lenses known from the above-quoted articles or prior art documents, still involves a high (expensive) expenditure even with the present state of the art in computer and manufacturing technology.
The present invention is based on the problem of providing a method of manufacturing progressive ophthalmic lenses whereof each is manufactured in correspondence with the individual data of a particular spectacle wearer, which are easy to match to the respective physiologic requirements of the respective spectacle wearer even when only one individualized progressive surface is used.
An inventive solution to this problem is defined in Patent claim 1. Improvements of the invention are the subject matters of claims 2 et seq.
The invention starts out from progressive ophthalmic lenses whereof each
presents a first surface having a defined surface power value (D1) in the surface apex, and
presents a non-spherical second surface (prescription surface) whose surface power (D2) varies along a line (referred to as principal line in the following) that follows at least approximately the main line of sight when the view is lowered, such
that the ophthalmic lens produces a first effect (Df) in a first reference point (BF), which is suitable for viewing in a first distance envisaged for the respective application, and
that this effect varies along the principal line by a predetermined value (addition Add) to a second value (DJ present in a second reference point, which is suitable for viewing in a second distance envisaged for the respective application, and whose second surface possibly presents a surface astigmatism optionally for partly compensating an ocular astigmatism and/or the astigmatism of oblique bundles.
The inventive method excels itself by the following steps of operation:
initially, ophthalmic lens blanks (blanks) are produced with a finished first surface in a defined particularly comparatively narrow-grading of the surface power value (D1)
starting out from the individual data, specifically at least the respective required first effect Df, the addition Add and possibly the value and the axial position of the ocular astigmatism of the spectacle wearer for whom the respective ophthalmic lens is intended, and on the basis of further design data, a first surface with a defined surface power value D, (that is possibly present only in the apex) is selected and the second surface is so computed that the surface power value D2f of the second surface, which is required in the first reference point, is adjusted in correspondence with the respective selected surface power D, of the first surface so that, as a function of the respective design data for one and the same first effect D, and one and the same addition Add and possibly also one and the same value and axial position of the ocular astigmatism, different pairings of first surfaces, which are distinguished from each other at least with respect to the surface power value D1 and of associated second surfaces computed on an individualized basis in each case are achieved.
The invention hence varies from the xe2x80x9cbasic rulexe2x80x9d applicable in the past in lens optics that always a single pairing of face surface and a surface on the side of the eyes is to be offered for a particular effect and for a special xe2x80x9cdesign familyxe2x80x9d. Due to the inventive approach to abolish this single pairing, substantially more degrees of freedom are achieved in the optimization of the progressive surface so that ophthalmic glasses or lenses, respectively, can be computed in a surprising mannerxe2x80x94even with a comparatively simple design of the face surfacesxe2x80x94which are better matched with certain individualized characteristics of the respective spectacle wearer than lenses for which only one respective bend of the face surface is chosen for each effect.
What is particularly preferred is the selection of the first surface as a function of the respective (individual) cornea/apex distance.
For the design data to be used for the selection of the first surface with the surface power value D1 in the apex, it is possible to refer moreover to the following aspects as a function of the respective weighting:
A particularly essential parameter for the selection of the bend of the face surface is, however, the cornea/apex distance because this distance is of decisive relevance for both the eyelashes hitting the glass and the imaging quality.
It is moreover possible to take further individual data of the respective spectacle wearer into consideration in the design data and additionally in the design of the progressive prescription surface.
These further individual data may be as follows:
pupil separation
length of the eye
forward inclination and chonchoidality
length or dioptric power ametropia
vertical and/or horizontal prisms and their right/left distribution
size and/or the shape of the chosen frame
centering height
pupil diameter and/or forward inclination of the lenses.
In particular, a spherical or a rotationally symmetrical non-spherical surface may be chosen as first surface.
It is furthermore also possible that a surface is chosen as the first surface whose principal sections are differently designed. It is possible that the first surface contributes a surface astigmatism appropriate for a partial or complete compensation of an ocular astigmatism and/or the astigmatism of oblique bundles. However, it is explicitly emphasized that a first surface with different principal sections is not necessarily chosen when an ocular astigmatism and/or the astigmatism of oblique bundles is to be compensated. A surface with different principal sections may also be chosen entirely independently of any astigmatism values whatsoever.
In particular, the first surface may present a stronger bend in the horizontal direction than in the vertical direction for cosmetic reasons. This is expedient particularly when the spectacle frame into which the lenses are to be mounted is substantially wider than high.
It is particularly preferredxe2x80x94even though not inevitably necessaryxe2x80x94that the first surface is the face surface. Hence, those machines may be used for the manufacture of the individual progressive surface, which are installed in so-called prescription lens manufacturing plants for the production of the concave surface.
The surface power D, of the first surface in the apex may be selected from the range between 0 dpt and 15 dpt.
The computation of the progressive surfaces may be carried out by the methods common in spectacle lens optics so that it need not be discussed here in more details. In particular, the computation can be carried out with target functions. In this manner, the initial visual acuity, models for the movements of the eyes and/or imaging defects of a higher order can be taken into consideration in the computation of the prescription surface.
It is moreover possible to take anisometropias into consideration in the computation of the prescription surfaces.
It is particularly preferable that the surface powers in the apex of the first surfaces inserted in total are graded in a scale of 0.25 dpt rather than in a coarse manner, with a grading by steps of 0.5 dpt still furnishing very good results.
For the entry of the individual data into the optimization program used for computing the progressive prescription surface it is particularly preferred that the individual data of the respective spectacle wearer as well as the surface design be graded with a defined scaling for the selection of the respective face surface and the surface on the sides of the eyes. The grading may be made in consideration of the ophthalmic optician""s possibilities to measure these values. The scaling may be as follows, for example:
It should be emphasized explicitly, however, that the aforementioned scale is by no means restrictive for the invention. It is also possible, of course, to use other scales as well for one part of the values or all values.
It is furthermore possible to define specific different surface designs for different applications. This may be achieved, for example, by the definition of an initial surface taken as starting point in the optimization. Such applications may be as follows:
standard (balanced in terms of distant vision, near vision and progression zone)
computer monitor workplace (mean distances preferred)
work at the desk (short distances preferred)
driving (non-symmetric design, wide distances preferred)
pilot (near vision part at the bottom and at the top)
sports and particularly ball-playing sports using a club (infinite up to roughly 1 m preferred)
watchmaker (very short distances)
surgeon (substantially average distances).
It should be explicitly emphasized that the above enumeration of surface designs is by no means final; it is rather possible to select the most different designs not mentioned here within the scope of the present invention.
With the inventive method it is furthermore possible that the position and the size of the individual vision ranges depend on the respective prescription. In particular, the position and size of the individual vision ranges may be different for hyperopia and myopia patients.
Further data may be taken into consideration in the inventive computation of the prescription surface:
It is possible, for instance, that the vertical spacing, the functional development of the dioptric power and of a possibly envisaged inset between the reference points in the distant and near vision ranges is chosen by physiologic and/or application-specific and/or frame-specific aspects. Moreover, the shape of the frame may also be considered in the design. It is even possible to consider the posture of the spectacle wearer and his customary vision in the designing work as well.
The surface on the side of the eyes, which is preferably the progressive surface, need not be a concave area in the strict sense of the word. It might be conceivable under certain circumstances that the surface power (and/or the line dioptric values) of the prescription surface assumes the value of 0 dpt at one site at minimum or even changes the sign.
It is possible in particular that the site where the 0 dpt value is reached or where the sign changes is located in the vicinity of the principal line.
The inventive method of manufacturing progressive ophthalmic lenses does not require that each individual ophthalmic lens be computed anew in all steps. It is rather possible that pairings between particular face surfaces and surfaces on the eye side are stored in a data base for the various surface designs and for respective typical user-specific data occurring frequently, from where they can be derived, and that the surface pairings and the data of the surface on the eye side are computed merely for less frequently occurring combinations when the order is received.
This database may store additionally empirically determined information about the compatibility, on the basis of which a choice is made among various surface combinations conceivable in consideration of the respectively employed optimization program and/or among various surface designs. In other words, the inventive method may be carried out with a xe2x80x9cself-learningxe2x80x9d optimization method.
It is preferred in any case that the ophthalmic lens blanks, which are produced with a finished first surface in a defined, comparatively narrow grading of the surface power (D1), are kept on stock.